Embodiments of the invention generally relate to reducing agents and methods for depositing a film on a substrate surface. In particular, embodiments of the invention are directed to reducing agents and methods for depositing a titanium film on a substrate.
Deposition of thin films on a substrate surface is an important process in a variety of industries including semiconductor processing, diffusion barrier coatings and dielectrics for magnetic read/write heads. In the semiconductor industry, in particular, miniaturization requires atomic level control of thin film deposition to produce conformal coatings on high aspect structures. For example, TiAl is a film that has been used in planar high-k metal gates in the 45 nm to 20 nm nodes.
Metal films (e.g., titanium) can be deposited by chemical vapor deposition (CVD) or cyclical deposition processes. For example, a substrate can be exposed to a mixture of a titanium organometallic precursor and a reducing agent. The reaction f the titanium organometallic precursor and the reducing agent results in the deposition of metallic titanium on the substrate surface. In a cyclical process, such as atomic layer deposition (ALD), the substrate is exposed to, for example, a titanium organometallic precursor which adsorbs or chemisorbs to the surface of the substrate. The titanium organometallic complex can be reduced to metallic titanium with a suitable reducing agent. In ALD processes, the metal precursor and reducing agent are separately exposed to the substrate to avoid the gas phase reactions used in a CVD process. Atomic layer deposition processes can result in the controlled deposition of a film having a known thickness.
The deposition of titanium alloy films is often accomplished by reduction of a titanium precursor containing chloride with an organometallic reducing agent. One common process for depositing a TiAl alloy involves the reaction of titanium tetrachloride (TiCl4) with an organoaluminum precursor to provide a film comprising titanium and aluminum. However, there is a need in the art for precursors and methods for depositing different intermetallic films.